1. Field of the Invention
The present invention relates to a monolithically integrated WDM demultiplex module in which a film wave guide is provided for guiding a light beam containing a plurality of wave lengths, a wave length selection element is provided for splitting the light beam and propagating in a defined direction the radiation components containing mutually different wave lengths and propagating in various directions, and a plurality of photodetectors are optically coupled to the film wave guide and respectively receive the individual radiation components containing mutually different wave lengths. 2. Description of the Prior Art
A module of the type set forth and a method for its manufacture are known in the art, for example, from the "Applied Physics Letters", Vol. 40, No. 2, Jan. 15, 1982, pp. 120-122. In this known module, the substrate is composed of silicon and the film wave guide is composed of As.sub.2 S.sub.3. A buffer layer SiO.sub.2 is located between the film wave guide and the substrate. The wave length selection element is composed of a grating introduced into the surface of the light wave guide, whose grooves extend obliquely relative to the propagation direction of the radiation propagating in the film wave guide. The radiation components propagating in various directions in the film wave guide following a grating and containing mutually different wave lengths are supplied to different photodetectors in the form of photodiodes. In this manner, each of the radiation components to which a separate wave length is assigned defines a wave length channel and a separate photodetector is assigned to each of these channels.
The manufacture of the above module occurs such that the buffer layer is first thermally generated on the surface of the silicon substrate and the film wave guide is then generated by vapor deposition in a vaccum. The photo diodes are fashioned in the form of Schottky diodes. The wavelength selection grating is written into the surface of the film wave guide by an electron beam.